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Integrated Design Developmentof a
Low MotionSemisubmersible Hull Form
Contents
• The Semisubmersible as a Deep water Concept
• Hull Form Development and Optimization
• Hull Motion and Structural Verification
• Platform Features
– Hull
– Topsides
– Mooring and Riser System
• Conclusions
The Semisubmersible as a Deep waterConcept
• System components adaptable to ultra-deep water
• Concept supports wide range of topside payloads
• Track record of proven design and fabrication and methods
• Proven offshore installation methods with minimal risk
• Quayside Hook-up and Commissioning
Advantages
Limitations
• Currently, the concept is limited to applications with subseawells
Hull Form Development
CONSTRUCTION
TRANSPORTATION
INSTALLATION
OPERATION
-
FunctionalRequirements
PracticalAspects
Hull FormOptimization
DesignVerification
TOPSIDES
DRILLING
PAYLOAD
RISERS
HULL
-
OPTIMIZEDMOTIONS ANDSTEEL WEIGHT
-
ANALYSIS
MODEL TESTING
-
Work Flow Path
Functional Requirements
Basis Range of Application
Location Gulf of Mexico Adaptable to other regions
Water Depth 1830 m > 3000 m
Topsides 100 KBOPD150 MMSCFDDrilling26,000 Tonnes
Can be re-configured for largertopsides (>40,000 Tonnes)
Riser System Steel Catenary Risers:6 Production2 Test2 Water Injection2 Export18-inch Maximum Dia.4,500 Tonnes vertical load
Flexibility to accommodate additionalrisers and/or larger diameter
Basic Requirements
Practical Considerations
Draft LimitationOperating Draft (Max.) = 27.5m
• Structural efficiency• Stability / tow-out draft• Deck Installation
Column ConfigurationFour-column and Six-Column configurations studied
Six-column solution selected:• Structural benefit from reduced deck span• Improved rectangular deck layout (safety, piping, etc.)• Increased flexibility for deck construction
Ring Pontoon
Omni Directional Motion Response
• Transit Draft (Min.) = 12m• Flexibility for Deck Integration• Access to yards
Hull Form Optimization
Variables
Draft
Columns (number, size,spacing, shape,inclination)
Pontoon (length, aspectratio, bilge radius, shape)
Cross bracing / ringpontoon configuration
Constraints
Target motion RAOs
Heave natural period
Motion/Acceleration at RiserAttachment
Minimum GM
Deck area requirement
Minimum trimming ballast
Pontoon span / depth ratio
Maximum Draft
Transit draft
SOLVER
HULLWEIGHTMODEL
MOTIONRESPONSE
MODEL
Cycle II I-O perat ing
0 .0 0 0
0 .0 0 1
0 .0 0 2
0 .0 0 3
0 .0 0 4
0 .0 0 5
0 .0 0 6
0 .0 0 7
0 .0 0 8
0 .0 0 9
0 .0 1 0
0 5 1 0 15 2 0 25 3 0 3 5 40
Pe ri od (s e c)
An
gu
la
rM
ot
io
n(
ra
d/
m)
Pitc h , Hd g = 0
Ro ll, Hd g= 9 0
Cycle II I- Operat ing
0 .0
0 .2
0 .4
0 .6
0 .8
1 .0
1 .2
1 .4
1 .6
1 .8
2 .0
0 5 1 0 1 5 2 0 2 5 3 0 3 5 4 0
Pe ri od(s e c )
He
av
e(
m/
m)
CG, Hdg = 0
CG, Hdg = 9 0
Pontoon We ight Coe ffic ients
P o ntoo n A spe ct R at io
Vol
ume
tric
Wei
ght
Coef
f.(t
/m3
)
D raf t = 2 2. 5 m
D raf t = 2 7. 5 m
D raf t = 3 2. 5 m
OPTIMIZED HULL
Hull Form Optimization
Morison Element formulation for heave pitchand roll motion
Added mass and inertia (wave) forcescalculated assuming hull as an assembly ofslender Morison elements
Closed-form equations for pre-integratedforces along longitudinal, transverse andvertical slender members
Motions are de-coupled by calculatingangular motions about an estimated center ofrotation
Special treatment (added mass corrections)at connections between elements andelement ends to obtain reasonablecorrelation with results from 3-D radiation /diffraction analysis
h_ toc
H_t ape r * (d raf t_r - Hp) d ra ft_r
Hp
Wpo
Xpon _Ytra ns * Yi
Yi
Xsp +Dco
Db _Dt * Dco Db_Dt *Dc i
Can t
r ad _col * Dco
r ad _col * Dci
Xsp
Xsp/3 Xs p/3
Ysp/2
Wpi
Dco
Wpx
p on_ Xtran s * XspDci
Motion Response Model
Example of Hull Idealization
Pontoon Weight Coefficients
Pontoon Aspect Ratio
Vo
lum
etr
icW
eig
ht
Co
eff
.(t
/m3
)
Draft = 22.5 m
Draft = 27.5 m
Draft = 32.5 m
Hull Form Optimization
Pontoon Aspect Ratio
a/b = 2 a/b = 3
Vo
lum
etr
icW
eig
ht
Co
eff
icie
nt
Increasing Draft
Steel Weights defined on a volumetricbasis
Correlated to actual and preliminarydesigns
Adjustments for draft / column (tankvent) height
Adjustments for pontoon height andaspect ratio
Steel Weight Calculation:
Hull Motion And Structural Verification
• Motion Response Prediction
• Comparison to Production Semi’s and MODU’s
• Model Testing
• Structural Verification
Hull Form - Key Features
• Six-columns
• Ring Pontoon
• Pontoon Shaped to ReduceMotion and Provide Omni-directional Response
• Enlarged Center Column andPontoon Section
• Pontoon Aspect Ratio MaximizesAdded Mass Contribution
• Pontoons Consist Entirely of FlatPlate Construction
• Columns Rounded to ReduceWave Run-up
Motion Characteristics
Heave Rao Pitch / Roll Rao
0.0000
0.0010
0.0020
0.0030
0.0040
0.0050
0.0060
0.0070
0.0080
0.0090
0.0100
0 5 10 15 20 25 30
Period (seconds)
Ro
ll/P
itc
hA
mp
litu
de
(rad
/m
)
Roll (Beam S eas)
Pitc h (Head Seas)
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
0 5 10 15 20 25 30
Period (seconds)
He
ave
Am
plitu
de
(m/m
)
0 deg (Head)
45 deg (Quartering)
90 deg (Beam)
Motion Performance Comparison
HEAVE MOTION @ CG, Hdg=90 (Beam Seas)
0.00
0.10
0.20
0.30
0.40
0.50
0.60
5 6 7 8 9 10 11 12 13
Tz (sec)
Sig
.Heave
/H
s(m
/m)
KBR Drilling and Production Semi
Production Semi 2
5th Generation Drilling Semi
Production Semi 1
Heave Rao Heave Response
100-YRHURRICANE
Heave RAO, Hdg = 90 (Beam Seas)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
0 5 10 15 20 25 30
Period (sec)
Heave
(m/m
)
KBR Drilling and Production Semi
Production Sem 2
Typical 5th Generation Drilling Semi
Production Semi 1
Motion Performance Comparison
Roll Rao Pitch Rao
Pitch R AO, Hdg = 0 (Head Seas)
0.000
0.001
0.002
0.003
0.004
0.005
0.006
0.007
0.008
0.009
0.010
0 5 10 15 20 25 30
Period (sec)
Pit
ch
(ra
d/m
)
K BR Drilling and P roduct ion Sem i
Typic al Pro duction S emi
5 th Generation Drilling Sem i
Roll RAO, H dg = 90 (B eam Seas)
0.000
0.001
0.002
0.003
0.004
0.005
0.006
0.007
0.008
0.009
0.010
0 5 10 15 20 25 30
Period (sec)
Ro
ll(r
ad
/m)
K BR Drilling and Product ion Semi
Typical Product ion Semi
5 th Generat ion Drilling S emi
Motion Performance Comparison
Heav e Acc eleration at Ris er P orch #2 , Hdg=45
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
5 7 9 11 13
Tz (se c)
Sig
.He
av
e.A
cc
'n/H
s[
(m/s
^2
)/m
]
Production Sem i #1
Production Sem i #2
KBR Drilling and Produ ction Semi
Vertical Acceleration At Riser Porch Locations
H eav e Acce leration at Riser Porch #1, Hdg= 45
0 .00
0 .02
0 .04
0 .06
0 .08
0 .10
0 .12
0 .14
5 7 9 11 13
Tz (sec)
Sig
.He
av
e.A
cc
'n/
Hs
[(m
/s^
2)/
m]
Product ion Semi #1
Product ion Semi #2
KBR Drilling and Production S emi
Model Test Verification
Heave Rao Correlation
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
0 5 10 15 20 25 30
Period (sec)
He
av
eA
mp
litu
de
(m/m
)
DIFFRACTION ANALYSIS
Model Test (soft mooring)
Model Test (full mooring)
Structural Design Process
Hull Framing and Scantling Calculations
Global Hull FE Model (Patran):
•Shell & Bulkhead Plating
•Pontoon & Column Web Frames
•Column Deck Flat Plating & Girders
•Shell and Bulkhead Stiffeners (“Lumped”)
•“Dummy” Members for Risers Porches, Fairleads,etc.
Static and Mooring/Riser Loads (Patran):
•Hull Dead Weight and Operational Loads, including Ballast
•Topsides Dead Weight and Operational Loads
•Mooring Line & Riser Tensions
Global Topsides Model (Patran):•Primary Transv erse Trusses
•Primary Longitudinal Trusses
•Primary Deck Girders and Plating
Hydrodynamic Analysis (WADAM)
•Various Wav e Headings & Periods•Map Wav e Pressures and InertialLoadsonto Global FE Model
Determine Design Waves
•“Squeeze-Pry” Load between the Pontoons
•Global Torsional Moment
•Longitudinal Shear Force between Pontoons
Global Strength Analysis (SESAM)
•Stillwater + Hydrodynamic Loads
•Yield Checks
•Buckling Checks (SESAM-Platework)
Fatigue Analysis (SESAM)
•“Screening” Lev elStochastic Fatigue Analysis using a BlanketSCF and one or more S-N Curv es with G.o.M Scatter Diagram
•Detailed Fatigue Analysis of Critical Areas using Refined FEModels (e.g. “t” x “t”)
123, 239
210,135
262, 672
368,602360,927
322, 958
Hull Structure
WebFrames
Transv. Bhd.Plating, Stiff &Girders
ShellPlating &Stiff.
Long. Bhd.Plating & Stiff.
Typical Pontoon Framing Scantlings in accordance with ClassRules (confirmed by GlobalStrength and Fatigue Analysis).
Shell Plate Thickness Limited to 22mm, except 30 mm in way of crosspontoon connections.
Plate thickness and stiffener sizevariations minimized (8 plates sizesand 7 stiffener sizes, excluding localreinforcement at foundations).
Option for bulb or angle stiffeners.
Frame Spacing: 2400 - 2950 mm.
Stiffener Spacing: 640-750 mm.
355 MPa (50 ksi) Materials.
Hull Structural Design
Global Structural Model
Hull design has adequate strength andmeets stress/buckling criteria usingreasonable plating and stiffener sizes
All areas have fatigue in excess of 200years (based on Gulf of MexicoCriteria)
Castings used in “corner” region toprovide sufficient fatigue life
Casting Detail
Moorings
Risers
Drilling Derrick
Accommodation& Utilities
Platform Configuration
TOPSIDES
Process Capacity: 100 KBOPD150 MMSCFD
Dimensions 60 x 96 x 14m
Number of Decks: 2
Operating Weight: 26,000 tonnes
HULL
Overall Length………...112 m
Overall Breadth………..95.2 m
Height (t.o. column)…..43.4 m
Draft……………………..27.5 m
Air Gap (to deck)..…….18.3 m
Process Facility
PF1C
VOID
PF1B
BALL AST
PF1A
BALL AST
PF2A
BALLAST
PF4B
BASE OIL
PF3A
BALLAST
PF5B
BALLAST
PF4A
DRILLWATER
PF5A
BALLAST
PF6A
BALLAST
ACCESS SHAFTW .T.
DOOR
SF1C
VOID
SF1BBALL AST
SF1A
BALLAST
SF2A
BALLAST
SF4B
BALLAST
SF3ABALLAST
SF4ABALLAST
SF5A
BALLAST
SF6A
BALLAST
A CCESS SHAFTW .T.
DOOR
CF1D
VOID
PA1C
VOID
PA1B
BALLAST
PA1A
BALLAST
PA2A
BALLAST
PA4B
BALLAST
PA3A
BALLAST
PA5B
BALLAST
PA4A
BALLAST
PA5A
BALLAST
PA6A
BALLAST
A CCESS SHAFT
ACCE SS SHA FTELEV.
SHAFT
P6B
BALLAST
S6BBALLAST
SF2BBALLAST
PF2B
FUEL OIL
PA2B
BALLAST
PUMPROOM
UTIL .
SHAFT
ELEV.SHAFT
PUMPROOM
UTIL .SHAFT
EL EV.
SHAFT
PUMPROOM
UTIL .
SHAFT
EL EV.SHAFT
PUMPROOM
UTIL .SHAFT
SA1A
BALLAST
SA2ABALLAST
SA4A
BALLASTSA3A
BALLAST
SA5A
BALLAST
SA6A
BALLAST
SA1B
BALLAST
SA2B
FUEL OIL
SA4B
BASE OILSA5B
BALLAST
SA1C
VOID
CA1D
VOID
SF5BBALLAST
Lower Hull Plan
CROSS PONTOONS(VOID TANKS)
PUMP ROOM (TYP)
ACCESS TUNNELS
FLUID STORAGETANKS (TYP)
Transverse Section At Corner Columns
ACCESSSHAFT
BALLASTTANK
PUMPROOM
VOID
VOID
EQPTROOM
CHAIN JACK
FAIRLEAD
VOID
PIPING/UTILITYCHASE
CROSS PONTOON
CHAIN LOCKERS
CHAIN PIPES
Transverse Section At Center Column
ACCESS TUNNEL
VOIDVOID
BALLASTTANK
BALLASTTANK
BULK TANKS
CHEMICAL
STORAGE
MUD TANKSDRILLING
FLUID
STORAGE
COLUMN STORAGE CAPACITIES
Barite/Bentonite…………425 m3 (15,000 ft3)
Cement……………………340 m3 (12,000 ft3)
Liquid Mud……………….4,000 bbls
Drilling Fluid (Brine)……4,000 bbls
Chemical Storage……….4,500 bbls
Topsides Configuration Alternatives
Integrated Deck
– Stiffened Plate “Box” Deck
– Floatover or Lifted Construction
Modular Deck
– Truss Structure
– Lifted in 4,000 ton modules orlarger
INTEGRATED “BOX” DECK
MODULAR DECK
Modular Deck Configuration
PROCESS MODULE
UPPER DECK
LOWER DECK
MEZZANINE DECK
PROCESS MODULE
Topsides - Upper (Weather) Deck
QUARTERS
RISERRACK
PIPERACK
PIPERACK SUBSTRUCT.
POWERGEN.
GASCOMPRESSION
CEMENTING/SACK STORAGE
DERRICK
FLARE
16.8 m 16.8 m19.75 m 19.75 m22.1 m
96 m
60 m
LAYDOWN/UTILITIES
FLASHGAS
BOOSTERPUMPS
Topsides - Lower (Production) Deck
QUARTERS
MUDPITS
MUDPUMPS
UTILITIES
MANIFOLD
OILPROCESS
AREA
WATERTREAMENT
UTILITIES
MCC/SWITCHGEAR
GASTREATMENT
Hull - Deck Interface
BOX BEAM
FE Model
Modular Deck Construction
Mooring And Riser System
EXPORTRISERS
PRODUCTION,INJECTION &TEST RISERS
MOORINGS
UMBILICALS
RISER PORCHES
Mooring System
SCR Interface - Production Lines
SCRFLEX JOINT/BASKET
CLEAR DECK AREA FORVERTICAL ACCESS
FIXEDPIPING
TO MANIFOLD
CHAIN JACK
CHAINBASKET
MESSENGER CHAIN
TOPSIDES
SCR LAYOUT CONCEPT
INSTALLATION SET-UP
Summary
The semisubmersible hull form provideslow motion characteristics within normaldraft limits and using a relatively simplehull geometry.
Motion response verified by analysis andmodel testing
Structural design and analysis to verifyhull weight and construction.
Efficient and functional deck layout.
Flexibility to accommodate alternativedeck construction methods.
Flexibility to accommodate riser system
Integrated Design Developmentof a
Low MotionSemisubmersible Hull Form
Thank You
Contacts